1. Field of the Invention
This invention relates to the field of fire-fighting equipment, specifically to means of fire fighting by a fire-extinguishing aerosol that is formed during burning of products made from pyrotechnical compounds.
Products made from aerosol-forming compounds are used in devices for fire fighting mainly in closed volumes, such as:
warehouses, garages and shop premises
vehicle compartments
2. Description of the Background Art
Efficiency of aerosol-forming fire-extinguishing compounds and products made from such compounds is assessed proceeding from its ability to meet a whole complex of requirements:
high fire-extinguishing efficiency at a minimum fire-extinguishing concentration;
low toxicity and explosion hazardness of burning products since they contain a minimum amount of underoxidated (NO, CO) and explosion-hazard (H2) components;
low burning temperature;
high level of deformation strength characteristics which makes it possible to avoid negative effects of various factors (vibration, impacts, temperature fluctuations) in transit and storage and to produce and use products with a minimum burning arch thickness;
a wide range of the compound burning velocity variation at atmospheric pressure, preferably without the use of special-purpose burn promoters and without
posing special high requirements for dispersity and fraction composition of source components;
low specific molding pressure which makes it possible to manufacture articles using a safe, low power-consuming and highly efficient production process.
Known pyrotechnical fire-fighting means consist mainly of the following components:
an oxidizer (generally nitrates or perchlorates of alkali metals and mixture thereof);
a burning binder selected from a series of epoxy or polyester resins, synthetic or natural rubbers, thermally plasticized rubbers and mixtures thereof;
production process and functional additives.
A fire-fighting compound is known (Patent RU 2095104, A . . . , Nov. 10, 1997) containing in percent by mass the following components: 1.5-1.8 burning binder; 5.0-20.0 coolant and the remainderxe2x80x94oxidizer. As a burning binder the following is used: 4-hydroxybenzoic acid or a mixture of 4-hydroxybenzoic acid and phenol-formaldehyde and epoxy resins, or a mixture of 4-hydroxybenzoic acid and epoxy resin, or a mixture of phenol-formaldehyde and epoxy resins, or a mixture of 4-hydroxybenzoic acid, phenol-formaldehyde and epoxy resins. As oxidizer it is allowed to use potassium nitrate or sodium nitrate, or potassium perchlorate, or sodium perchlorate, or a mixture thereof. Dicyandiamide or melem, or melamine, or urea, or urotropin, or azobisformamide or mixtures thereof are used as a coolant. The compound can also contain production process additives and burning promoters at a rate of 0.1-5.0% by mass.
The compound production method includes charging of a mixer with an oxidizer, burning binder, production process additives and burning promoters and mixing them for one hour. According to example 3 the compound consisting, % by mass, of potassium nitratexe2x80x9460; sodium nitratexe2x80x948; 4-hydroxybenzoic acidxe2x80x949; phenol-formaldehyde resinxe2x80x948; dicyandiamidexe2x80x9412; CuOxe2x80x942; and polytetrafluoroethylenexe2x80x941, shall be mixed in a mixer for one hour. After this the resulting mass shall be used to form articles of required geometry by the method of blind die pressing at specific pressure 1500 kg/cm2 (150 MPa).
The compound and its production method have a serious drawback lying in the fact that in order to ensure its practical utilization of the compound, charges shall be pressed at high specific pressure 1000-1500 kg/cm2(100-150 MPa). This requirement results, on the one hand, in enhanced hazard in processing the compound and, on the other hand, the high level of specific pressure during the compound processing makes it possible to apply a more efficient, safe and less power-consuming production process of the compound pressure by the method of continuous pressing using a screw press.
Compounds made by the blind die pressing are characterized by enhanced brittleness even at room temperature. Relative deformation value at rupture does not exceed 2%.
The most close analogue is the compound and the method of its production protected by patent RU 2005517, A . . . , Jan. 15, 1994. According to example 1 the compound includes, % by mass, KClO4xe2x80x9439.5; KNO3xe2x80x9438.5; PVA (polyvinyl acetate)xe2x80x948.8; dibutyl phthalatexe2x80x943.5; iditolxe2x80x945.0; liquid petrolatumxe2x80x941.0; KClxe2x80x941.0; carbonxe2x80x940.2; polytetrafluoroethylenexe2x80x941.5; and stearatexe2x80x941.0.
The compound production method includes mixing pure PVA (and only after this adding to the mixer up to 10% of water) or adding in two or three steps a 30-35% water dispersion containing KClO4, KNO3, and KCl. The mixture shall be stirred for 20-30 minutes and then all the additives shall be added. After this the mixture shall be stirred at a negative pressure for one hour. The processed semi-finished product shall be discharged from the mixer and passed for rolling. The semi-finished product shall be rolled from 12 to 20 times at 70-90xc2x0 C. to make it flat. The flat product shall be folded and passed to formation operation on a hydraulic press at 60-90xc2x0 C. and a pressure not less than 1000 kgf/cm2 to obtain round blanks of up to 70 mm in diameter, with or without a channel.
This compound and the method of its production have several significant shortcomings:
high fire-extinguishing concentration of the compoundxe2x80x9427 g/m3;
high specific pressure required to form articles from the compoundxe2x80x94at least 1000 kgf/cm2 (100 MPa);
unsteady burning of the compound (at a pressure of 2-20 at it is necessary to add such special-purpose burning modifiers as carbon);
unsteady inflammation due to residual moisture content of the main aerosol-forming ingredients (KClO4, KNO3). Moisture of the KClO4, KNO3 particles results in impaired adhesion of them to the polymeric binder surface and this, in its turn, leads to a drastic decrease in the strength characteristics of the finished product.
The indicated shortcomings depend on chemical characteristics of used components and their mass ratio. During combustion high and unbalanced content of combustibles in the compound leads to underoxidation of decomposition products of the main (PVA) and additional (iditol) burning binder because of insufficient quantity of oxidizer""s oxygen. Hence it follows high content of toxic underoxidated and explosion-hazard gases in products of burning, unsteady inflammation and combustion of the composite. Because of technological problems selection of the burning binder pair: main (PVA) and additional (iditol) leads to a necessity to use PVA water dispersion. That leads to KClO4 and KNO3 moistening, and as a result to instability during the composite inflammation and combustion, impossibility to reach high level of deformation strength characteristics of the composite, to a necessity to use high specific molding pressure.
This invention solves the following technical tasks:
ensuring of burning stability and increasing burning velocity and, hence, enhancing gas and aerosol formation speed;
enhancing the level of deformation strength characteristics;
decreasing the fire-extinguishing concentration;
decreasing level of toxicity and explosion risk of the burning products due to decrease of content of fraction of incompletely oxidized and explosion hazard gases;
decreasing the specific pressure of the compound formation and, as a consequence, lowing the hazard level and also making it possible to use highly efficient and less power-consuming production process using the continuous pressing method.
The technical tasks are solved by using the new composite and the claimed method of its production.